Holothuria (Lessonothuria) insignis Ludwig, 1875

Ahmed, Quratulan, Thandar, Ahmed S. & Ali, Qadeer Mohammad, 2020, Holothuria (Lessonothuria) insignis Ludwig, 1875 (formally resurrected from synonymy of H. pardalis Selenka, 1867) and Holothuria (Lessonothuria) lineata Ludwig, 1875 - new additions to the sea cucumber fauna of Pakistan, with a key to the subgenus Lessonothuria Deichmann (Echinodermata: Holothuroidea), Zootaxa 4767 (2), pp. 307-318 : 309-310

Holothuria (Lessonothuria) insignis Ludwig, 1875

Figure 2

Holothuria insignis Ludwig, 1875: 106 , p1.7, fig.28.

Holothuria pardalis var. insignis Sluiter, 1890: 106 .

Halodeima insignis Heding, 1934: 23 .

Holothuria (Lessonothuria) insignis Rowe, 1969: 149 (passim); Clark and Rowe, 1971: 176 (distrib.), p. 194 (note); Samyn, 2003: 42 (passim); Samyn et al. 2019 (in remarks and key).

Holothuria (Lessonothuria) pardalis Rowe & Gates, 1995: 292 (partim);? Cherbonnier, 1988:117, fig.47.

?non Holothuria (Lessonothuria) insignis Thandar 2007:16 , text fig. 6 (=? H. lineata Ludwig, 1875 ).

Material examined. Sunahri Beach, 24º 52’33.49’’ N, 66º 40’40.20’’ E, Holo. 19, rocky shore, 24 November 2014, 1 spec.; Buleji, 24º 50’20.41’’ N, 66º 49’24.15’’ E, 15 April 2015, 1 spec.

Habitat. The specimens were found attached to a rock in the intertidal zone. This species inhabits the lower mid-littoral zone on rock and sand substrate, living under boulders or hides in sand in shallow waters.

Description. Specimen from Sunahri beach was 80 mm long whereas the specimen from Buleji measured 60 mm. Both specimens are cylindrical with the dorso-ventral surfaces well arched. Colouration of live specimens was dark brown dorsally ( Figure 2A ) with the ventral surface light brown to creamy-white with brown blotches ( Figure 2B ).The dorsal body wall is only slightly thick but rough to touch. Podia are scattered over the entire body surface with the dorsal ones tipped light creamy-brown. The mouth is ventral and encircled by 18 tentacles ( Figure 2C ) and the anus terminal, encircled by six papillae. Both the Polian vesicle and stone single are single but the madreporite was not observed. Cuvierian tubules are present.

Body wall ossicles comprise tables ( Figure 2D ) and pseudo-buttons, the latter often slightly knobbed ( Figure 2E ). The tables, 20–86 µm, have a squarish or rounded disc usually perforated by the four central holes, rarely more and with a very spiny margin. The spire is stunted or drastically reduced, terminating in a few teeth, or absent, then teeth appear to be present on disc only; the spire terminates in usually eight teeth surrounding a central hole. Dorsally and ventrally the pseudo-buttons, 20– 13 µm, are both regular (complete) and irregular (incomplete) with the latter predominating. The ventral podia are supported by elongated rods, 88–274 µm, perforated with 1–2 holes at each end ( Figure 2H ). The end plates of the ventral podia, 34–110 µm, are surrounded by elongated plates with undulating margin and paired series of large holes ( Figure 2F ); the dorsal podia have similar but slightly shorter rods (2I), 38–234 µm. The tentacle rods, 30–52 µm, may be branched at one end and perforated at the other (2G).

Remarks. Holothuria (Lessonothuria) insignis Ludwig, 1875 was not reported from the Pakistan coast before and hence it is new to the fauna of Pakistan. The specimens are similar to those described by Ludwig (1875) from Bowen ( Australia), Lampert (1896) from East Africa, and recently by Samyn et al. (2006) from the Comores, and Afkhami et al. (2015) from the Persian Gulf ( Hormuz Island). Their specimen size-range varied from 20–80 mm with the dorsal life colouration described as darkish grey or brown, striped brown, and ventral life colouration whitish.

Clark and Rowe (1971) recorded this species from the Red Sea, Eastern Africa and Madagascar, Bay of Bengal, East Indies, north Australia, Philippines, China, south Japan and south Pacific Is. Heding (1934) reported on some holothuroids from Hong Kong which included H. insignis which he was convinced differs significantly from H. pardalis . Ducarme (2016) reported H. insignis among 14 species of sea cucumbers encountered during the survey of nearby atolls in the Maldives.

Although Clark & Rowe (1971) included both H. pardalis and H. insignis , in their note on p. 194, question the validity of the latter but because of Heding’s (1934) viewpoint, retained it as a valid species. Later, however, Rowe (in Rowe & Gates 1995) accepted H. insignis in the synonymy of H. pardalis , after examining some type material and numerous specimens from various museums and localities. A study of the ossicles of a syntype (ZMH E2573) by AST, received from Dr Samyn, revealed that the table discs of H. insignis usually have four central holes, hardly any marginal holes, a remarkably reduced or absent spire and with most of the buttons (ca. 60%) incomplete, or often developed with a single series of three holes on one side, not showing any sign of reduction, or are sometimes reduced to C-shaped rods, but rarely twisted. Complete buttons have three pairs of slit-like holes and rarely small terminal holes and are deeply constricted in the middle. The rods of the papillae are expanded at ends which may bear perforations or the rods are just thick, curved structures without perforations or spines. Rods of the ventral podia are straight or slightly curved, sometimes spinose, with 3–7 holes at each end. Plates associated with end plates of the ventral podia appear rounded or slightly elongated with undulating, sometimes spinose margin, with large paired series of holes unlike the plates found in H. lineata , which have a convincingly spinose or serrated margin. Hence, we opine that there is enough morphological evidence to resurrect H. insignis from the synonymy of H. pardalis . This evidence is here summarized in Table 2 , which compares both species. The ossicles of H. pardalis are illustrated in Figure 3 for the purpose of comparison. The fact that some specimens of H. insignis do show some plates associated with the end plate with also serrated margins as in H. lineata , these may be a result of hybridization, as both species are sympatric over a wide range wherever they occur, or some other factors. In this light Thandar’s (2007) H. insignis , which was later transferred to H. lineat a, needs re-examination on the bases of new materials and the characters here recorded, taking into account the re-description of the syntype of H. lineat a by Samyn et al. (2019), as it might represent a true H. insignis .

Figures

FIGURE 2. Holothuria (Lessonothuria) insignis Ludwig, 1875. Holo. 19. A. Dorsal view; B. Ventral view; C.Anterior end with extended tentacles; D. Tables of dorsal integument E. Regular and irregular pseudo-buttons of integument; F. Plate from ventral tube foot; G. Rod of tentacle; H. Tube feet rod; I. Papillae rods; J. Part of calcareous ring (single dorsal radial and adjoining interradial plates)

FIGURE 3. Holothuria (Lessonothuria) pardalis Selenka, 1867. A. Dorsal view; B. Pseudo-buttons from body wall; C. Tables from body wall; D. End-plate; E. Podial rods; F. Rods of tentacles; G. Part of calcareous ring (single dorsal radial and adjoining interradial plates).